Acid treatment of oils



D. D. STARK ET AL ACID TREATMENT 0F OILS Sept. 41, 1936.

original Filed April 22, 1931 JN T N Nr R J m m5 T K A fw/A... fm 5;. f2

Patented Sept. 1, 1936 UNITED STATES PATENT OFFICE som TREATMENT or oms Application April 22, 1931, serial No. 532,000 Renewed June 10, 1935 10 claims. (c1. 19e-s1) Ths invention relates to the acid treatment of oils and has for its principal object the eiiicient utilization of acid for the removal of impurities from hydrocarbon distillates, or fractions.

In the treatment of oils of high sulphur content, such as a pressure distillate made by cracking high sulphur residuums or gas oils, the removal of sulphur compounds requires large quantities of sulphuric acid (66 Baum or stronger).

We have found that acid sludge, resulting from the treatment of oil with fresh acid, when used as a reagent for the removal of sulphur compounds has a selective affinity therefor similar to fresh acid. This results in a large saving of fresh acid in the treatment of oils by a series of steps for removing sulphur compounds first from a distillate by the use of acid sludge prior to contacting the thus treated distillate with fresh acid, the acid sludge used in the rst step being derived from a succeeding step.

In order to utilize the acid sludge and fresh acid to the greatest possible extent, a countercurrent system of contacting an oil with acid reagents is best adapted for the process in combination with the use of contact material, such as Raschig rings, for contacting, coagulating, and settling of the acid sludge from the oil.

We have found that by at least twice using the acid sludge resulting from the treatment of a pressure distillate with fifteen pounds of 66 sulphuric acid per barrel, that the oil after redistillation has the same sulphur content as if it had been treated with about pounds, or more, per barrel of fresh acid in a batch treatment.

It is quite evident that the governing factor in the treatment of pressure distillate with acid sludge is the number of stages of application, hence the optimum effect can be obtained by a truly counter-current acid treating system which represents sludge treatment in a plurality of stages. 'Ireating with the same rate of fresh acid in a two or three stage circulatory system provides a finished gasoline after redistillation having appreciably more sulphur content than a gasoline from pressure distillate treatedby a counter-current system and redistilled.

In our treatment of distillates requiring the use of 66 sulphuric acid, or stronger, in order to prevent chemical reactivity with unsaturated hydrocarbons and to counteract exothermic chemical reactions, we control the temperatures throughout the process by refrigerating the oil and acid mixtures and providing a temperature therefor of from 40 F. to 20 F., or less. Such cold treatment aids in the reduction of the sulphur content because it permits the reaction of a larger percentage of the sulphuric acid with sulphur compounds present in the distillate.

A form of our process is illustrated in the diagrammatic sheet of drawings wherein an oil, such 5 as a pressure distillate, is taken from storage I0 and forced by pump Il at any particular temperature through a cooler I2 into the bottom of a third contact chamber I3. Said chamber I3 is partly filled with contact material I4, preferably 10 in the form of Raschig rings about one inch diameter, which extend from the lower broken lines up to a point in the chamber where the upper surfaces will be exposed to theaction of an acid spray I5 supplied with acid sludge by a pump I6 l5 from the bottom of a second contact chamber 2 I.

Valves Il and I8 are provided to by-pass chamber I3, or the acid treated oil therefrom is supplied through aline I9 and cooler 20 to the lower part of a second contact chamber 2I which is 20 similarly constructed to chamber I3 for the purpose of treating the cooled oil with acid sludge supplied from the bottom of a first contact chamber 26 by a pump 22 through an acid spray 23, the treated oil passing through a line 24 and cooler 25 25 to the lower portion of chamber 26.

In chamber 26, the oil which has been treated once or more with acid sludge for the removal of sulphur compounds is contacted with .fresh acid. supplied by a pump 21 through a spray 28 and the 30 treated oil passes through a line 29 to the lowerY part of a settling chamber 30 passing upwardly therein through contact material whereby the acid sludge particles are coagulated and settled out to be supplied to pump 22, as indicated in our copending application, Serial Number 489,870, filed October 20, 1930. While chamber 30 is desirable as a safety factor, yet it may be bypassed, as by proper handling the same quantity of acid sludge may be coagulated and removed in chambers 2| and 26.

The treated oil, distillate, passes from settling chamber 3l) and contains substantially no acid and then flows through a line 3| to the lower part l of a contact chamber 32 wherein it meets a. 45 counter-current flow of caustic solution supplied through a pump 33 and spray 34 from the bottom of contact chamber 35, any spent caustic with contained impurities being passed through a line 36 to be wasted, or other uses.

In chamber 35, the oil ls contacted with fresh caustic solution supplied through a line 31 and the neutralized oil then iiows through a line 38 to the lower part of a wash chamber 39 wherein it is washed with water from a line 40 and the finished 55 distillate is passed to storage, or use, through a. line 4|.

All the chambers I3, 2|, 26a 30, 32, 35, and 39 may be of equal size and all except 39 maybe lled with contact material as described, but all the acid chambers I3, 2|, and 26 must be filled with such contact material.

Heretofore, the principal objection to continuous treating systems has been the inability to insure uniform distribution of the treating medium over a cross section of the contacting vessel, but the success of such system depends partly on the construction of apparatus for'bringing the material to be treated in uniform contact with the-treating'medium of increasing strength, or concentration.

In the present system, this is accomplished by giving pump IB a greater capacity than required for the sludge alone from chamber 2| whereby an internal *circulating pathV of sludge and oil is set up through spray I5 (which may be a well known type of diffusion ring), chamber I3, pipe I9, cooler 20, chamber 2| and pump I6. Such internal circulation gives a constant ratio of acid sludge to oil, the excess sludge coagulating and settling out uniformly over the cross section of contact :material under spray I5 where it settles downwardly becoming more spent in ycontacting oil of 'increasing impurity.

Additionally, pump 22 is part of a similar circulating system and other units may be= added if desired. Such described internal circulating systems have the addedadvantages of increasing the heat exchange efliciency of the coolers over a wider range of treating plant capacities and insure intimacy of contact between the oil and treating agent at these points.

The contacting is accomplishedY by mechanical mixing (as in the pumps) and by surface contacting, a proper velocity of oil being maintained through the contact material to assure coagulation, settling and 4removal of the vacid sludge, while the internal circulation gives increased cooling eiciency by increasing the velocity of the oil through the coolers.

Regulation of the pressure on the system is accomplished by manipulation of valves 42, 43, and 44.

lIhe whole system described comprises a counter-current treatment for a continuous flowl of distillate whereby a plurality of stages of treatment with acid sludge insures a removal of sulphur compounds with a. minimum content ofA fresh acid, and in which at least two stages of internal circulation are desirable to provide intimate contact of the materials at all times partly through the mediuml of even distribution of the acid reagent over the contact material and by lmeans of the material itself.

However, with the system described, a similar counter-current flow, either in single kor multiple tower arrangement, may give suilicient contacting to produce the maximum desulphurization at a point where theacid sludge is just fluid enough at the temperatures employed to ilow under a small pressure head. In this manner a maximum. use

of the acid sludge is procured in a counter-current be desirable to cool and treat the oil at a temperature as low as 20 F.

Likewise, it is advisable to maintain pressure on the system to prevent excess gasication on account of the reaction of oil and acid producing quantities of sulphur dioxide. By maintaining a gage pressure up to pounds per square inch (preferably from 50 to 60 pounds) at a temperature of 40 to 50 F., the S01l will be maintained in liquid phase, which assures a minimum formation -of gas which otherwise might increase the velocity of the distillate to such a point as to prevent coagulation and settling of the acid sludge. y

We claim as our invention:

1. A process of treating oil which comprises: continuously passing a stream of hydrocarbon oil through a plurality of chambers in series containing contact material and continuously passing sulphuric acid and acid-sludge in counter-current flow to said oil, removing a substantially-acid free oil from the last chamber in the series; the acid-sludge being passed continuously with part of the oil from the lower porvtion of one chamber to the upper portion of a preceding chamber wherein the acid sludge separates from the accompanyingoil to be sprayed on and descend by gravity through the contact material in said chamber, and the entire system being held under a superatmospheric pressure of from 50 to 60 pounds per square inch.

2. A process of treating oil which comprises: continuously passing a stream'of hydrocarbon oil through a plurality of chambers in series containing contact material and continuously passing sulphuric acid and acid-sludge in countercurrent ow to said oil, removing asubstantially acid free-oil from the last chamber in the series; the acid-sludge being passed continuously with part of the oil from the lower portion of one chamber to the upper portion of a preceding chamber wherein the acid-sludge separates from the accompanying oil to be sprayed on and descend by gravity through the contact material in said chamber, and the entire system being held under a superatmospheric pressure suiicient to hold SO2 in liquid form at the operating .temperature. l

- 3. A process of refining oil which comprises:

.continuously passing a stream of hydrocarbon Y its passage from the upper part of one chamber to the lower part of a succeeding chamber, wherein the oil ows upwardly through the contact material while meeting a downward ow of acid and acid sludge, by the addition of a portion of the oil carrying acid sludge passed from the lower part of said succeeding chamber to the upper part of said first chamber wherein said acid sludge separates from said carrying oil to descend by gravity through the contact material in said rst chamber.

4. A process of rening oil which comprises:

4continuously passing a stream of hydrocarbon oil through a plurality of chambers in series containing contact material and continuously passing sulphuric acid and acid-sludge therethrough in counter-current ow to said oil, the volume of said stream of oil being increased in its passage from the upper part of one chamber to the lower part of a succeeding chamber,

wherein the oil ows upwardly through the contact material while meeting la downward ilow of acid and acid sludge, by the addition of a portion of the oil carrying acid-sludge passed from the lower part of said succeeding chamber to the upper' part of said rst chamber wherein said acid-sludge separates from said carrying oil to descend by gravity through the contact material in said rst chamber, and the temperature of said increased stream being reduced by cool--v ing intermediate said chambers to a degree sufcient to cause increased selective reaction of the acid sludge with sulphur compounds in the oil.

5. A process of reiining oil which comprises: continuously passing a streamof hydrocarbon oil through a plurality of chambers in series containing contact material and continuously passing sulphuric acid and acid-sludge therethrough in counter-current flow to said oil, the Volume of said stream of oil being increased in its passage from the upper part of one chamber to the lower part of a succeeding chamber, wherein the oil ows upwardly through the contact material while meeting a downward iiow of acid and acid sludge, by the addition of a portion of the oil carrying acid-sludge passed from the lower part of said succeeding chamber to the upper part of said lrstchamber wherein said acid-sludge separates from said carrying oil to descend by gravity through the contact material in said first chamber, and the temperature of said increased stream being reduced by cooling intermediate said chambers to about between 20 F. and 40 FL 6.'A process of refining oil which comprises:

continuously passing a stream of hydrocarbon oil through a plurality of chambers in series containing contact material and continuously passing sulphuric acid and acid-sludge therethrough in counter-current iiow to said oil, the volume of said stream of oil being. increased in its passage from the upper part of one chamber to the lower part of a succeeding chamber, wherein the oil flows upwardly through the contact material while meeting downward ilow of acid and acid sludge, by the addition nf. a portion of theoil carrying acid-sludge passed from the lower part of said succeeding chamber to the upper part of said rst chamber wherein said acid-sludge separates from said carrying oil to descend by gravity through the contact material in saidrst chamber and the entire system being held under a superatmospheric pressure sufficient to hold SO2 in liquid form at the operating temperature.

7. A process of refining oil which comprises: continuously passing a stream of cracked gasoline through a plurality of chambers in series containing contact material and continuously passing sulphuric acid and acid sludge therethrough in counter-current iiow to said gasoline; the velocity of said stream of gasoline being increased in its passage from the upper part of one chamber to the lower part of a succeeding chamber, wherein the gasoline iiows upwardly through the contact material while meeting a downward ilow of acid and acid-sludge, by the addition of a portion of the gasoline carrying acid-sludge in a constant ratio of gasoline'to acid-sludge passed from the lower part of said succeeding chamber to the upper part of said first chamber wherein said acid-sludge is -separated from said carrying gasoline to descend by gravity through the contact material in saidrst chamber.

8. In the process of rening hydrocarbon oils with sulphuric acid wherein the acid is passed downwardly through a chamber substantially iilled with contact material having relatively free drainage, the oil is simultaneously passed upwardly therethrough, and the resulting drained acid sludge is removed from the chamber at a rate sufficient to prevent substantial accumulation therein, that step which comprises: owing the oil upwardly through said contact material wet with the acid in said chamber but through no substantial body of the acid in said chamber.-

9. In the process of reiining hydrocarbon oils with sulphuric acid wherein a stream of oil is passed through successive chambers each substantially filled with contact material having relatively free drainage, sulphuric acid and acid- /with sulphuric acid wherein a stream of oil is passed through successive chambers each substantially lled with contact material having relatively free drainage, sulphuric acid and acidsludge is passed through said chambers in counter-current ow to said oil, and acid-sludge is removed from the lower part of each chamber, that step which comprises: continuously cycling a' secondary stream of oil from the lower part of one chamber to the upper part of a second chamber thence back to the lower part of the rst chamber at a velocity suiiiciently great enough to remove acid-sludge and prevent substantial accumulation of the drained acid-sludge in the first chamber while locally decreasing such velocity in the upper part of said second chamber sufficient to cause separation of the acid-sludge from said secondary stream to be deposited on the contact material in said upper part.

DAVID DEWEY STARK.

THOMAS OLIVER EDWARDS, Jr. 

